Flood Risk & Drainage Requirements for the Royal Borough of Greenwich

The Royal Borough of Greenwich decides applications against Policies E2 (Flood Risk) and E3 (Residual Flood Risk) of its Core Strategy, adopted in July 2014, and as Lead Local Flood Authority it reviews the drainage itself. The requirement that reaches furthest is in the June 2025 validation list. It asks for a flood risk assessment on Flood Zone 1 sites where surface water is mapped 0.3 m deep, or that sit within 100 m of a recorded sewer flood.

Those buffers reach streets a long way from the Thames. A house extension in Eltham can need an assessment, and a small block of flats in Plumstead a SuDS strategy as well, even where the national flood map shows the site in Flood Zone 1. This page sets out Royal Greenwich flood risk and drainage requirements, including those of the bodies the council consults, which documents carry each one, and how we meet them. To talk through a site, call 01293 214444 or email enquiries@unda.co.uk.

Which Local Plan decides a Royal Greenwich application in late 2026?

The adopted plan is still the Royal Greenwich Local Plan: Core Strategy with Detailed Policies, adopted on 30 July 2014. Its flood policies, E2 and E3, are the ones a decision has to follow, read alongside the London Plan 2021 and the August 2026 NPPF.

A replacement is well advanced. The council published the draft Royal Greenwich Local Plan to 2040 at Regulation 19 and consulted on it from 27 July to 6 September 2026. Its Local Plan page says the representations are being reviewed and that the council expects to submit the plan for examination by the end of 2026; the Local Development Scheme (December 2025) puts the hearings in spring 2027 and adoption at the end of 2027. In the draft, Policy EN6 (Managing Flood Risk) and Policy EN7 (Sustainable Drainage) would take over from E2 and E3.

For an application going in now, that means two sets of tests. E2 and E3 decide the case. Draft EN6 and EN7 carry growing weight as the plan moves through examination, and on a scheme that will not be decided until 2027 an officer can reasonably ask how it measures up against them. We write to both, so a layout fixed in 2026 does not have to be reworked when the new policies are adopted.

The London Plan is in the same position. A draft new London Plan was consulted on from 16 July to 15 October 2026; until it is published, Policies SI 12 and SI 13 of the 2021 plan remain the strategic tests.

Who has a say on flood risk and drainage when you apply to Royal Greenwich

One council holds both local roles. There is no county tier in London, so the borough that decides the application is also the Lead Local Flood Authority that comments on its drainage, and no internal drainage board covers any part of it.

Because the flood team sits inside the same council, a drainage objection goes straight onto the planning file instead of arriving later as a condition to tidy up. The guide to an LLFA objection explains how one is answered.

Royal Greenwich flood and drainage policies, adopted and draft

Four adopted policies set the tests today: two from the 2014 Core Strategy and two from the London Plan. The two draft policies sit below them in the table with their stage, because a decision in 2027 may turn on them.

Requirements checked November 2026.

Policy E2 (Flood Risk): what Royal Greenwich requires

Policy E2 makes the council's SFRA the starting point for every flood decision and asks for a flood risk assessment that deals with every source. Its opening reads: “The Royal Borough's Strategic Flood Risk Assessment must be used to inform development and reduce flood risk in Royal Greenwich by: i. Applying the sequential and exceptions tests as detailed in the National Planning Policy Framework and accompanying Technical Guidance; ii. Demonstrating consideration of all forms of flood risk by preparing flood risk assessments, in line with advice from the Environment Agency.” (Core Strategy, 2014)

The assessment then has to show six things: that the consequence and probability of flooding are reduced where possible with no increase elsewhere; how actual and residual risk are managed over the lifetime of the development with climate change; that layout, form and floor levels keep the building safe; that there is dry access, egress and refuge, with emergency planning considered; that the floodplain still works; and that the tidal and fluvial defences are safeguarded. The supporting text (paragraph 4.6.24) is where the Flood Zone 1 triggers come from: sites over one hectare, surface water 0.3 m deep or more, and the 100 m sewer and 250 m groundwater buffers that the validation list repeats.

The policy lists six points, and an assessment is quickest to check when it follows them. Our report answers each one under its own heading, quotes the SFRA data the answer relies on, and states the floor level, the access route and the source of every flood level in figures, so nothing has to be inferred.

Policy E3 (Residual Flood Risk) on the defended riverside

Policy E3 applies where the land is defended but would flood if a wall failed, and it turns the flood risk assessment into a set of levels. In the words of the Core Strategy: “Applicants, as part of their flood risk assessment must provide details of indicative breach flood water levels, ground levels, ground, first and second floor levels in metres AOD, and show the floor level for bedrooms and safe refuges, providing justification for the options chosen.” A flood plan with evacuation and response procedures is required as well (Core Strategy, 2014).

The supporting text names the places a breach would hit hardest: Thamesmead, New Charlton and the Greenwich Peninsula, with the eastern areas most exposed because the ground is low and the canals carry water inland. The July 2026 SFRA maps the Environment Agency's Thames breach models, the 2017 model upriver of the Barrier and the 2018 model downriver, so the depth, hazard and velocity for a given site are already published. Our assessment reads those values for the site, sets the bedroom and refuge levels above them, and writes the flood plan around the access route the SFRA shows staying dry. The residual flood risk explainer covers the principle.

London Plan Policy SI 12 (Flood risk management) and Policy SI 13 (Sustainable drainage)

Both London Plan policies sit over every Greenwich decision. SI 12 asks that “Development proposals should ensure that flood risk is minimised and mitigated, and that residual risk is addressed”, and part F expects buildings next to flood defences to be set back from them so the defences can be maintained and raised. SI 13 asks that “Development proposals should aim to achieve greenfield run-off rates and ensure that surface water run-off is managed as close to its source as possible”, through a hierarchy that runs from rainwater use down to “controlled rainwater discharge to a combined sewer” (London Plan 2021, chapter 9).

Greenwich's validation list cites SI 13 for the SuDS strategy, and the council's Climate Resilience SPD, adopted on 25 March 2026, repeats that new development should reach greenfield rates following the SI 13 hierarchy. A drainage strategy that goes straight to the sewer meets neither document; ours records why each higher step does or does not fit the site, with the ground investigation or the outfall survey behind it. The SuDS hierarchy guide goes through the steps.

Draft Policy EN6 (Managing Flood Risk): what the new plan would change

Draft Policy EN6 in the Regulation 19 plan widens the flood risk assessment triggers and puts hard limits on some uses. Part 5 would require an assessment where the site is in Flood Zone 2, 3a or 3b or a Critical Drainage Area as defined in the SFRA, is larger than one hectare, is major development in Flood Zone 1, or “increases the number of habitable units, or proposes sleeping accommodation, below ground level”. Part 7 is the strictest line in the draft: “Development proposing highly vulnerable uses in Flood Zone 3 and Critical Drainage Areas will not be permitted.” (Regulation 19 draft, chapter 8)

The rest of draft EN6 is about distances and levels. It would require an 8-metre buffer from the top of bank of fluvial watercourses and culverts, a 16-metre set-back from the most landward part of the tidal defence, buried elements included, finished floors 600 mm above the design fluvial level, sleeping accommodation above the design tidal level including breach and climate change, and a construction drainage strategy on major schemes. The reasoned justification (8.90) lets a site allocated in the new plan skip a site-specific sequential test where the use matches the allocation and the risk has not changed; windfall sites follow section 6 of the SFRA. A layout that clears E2 but puts a building 10 m from a river wall should be checked against the 16 m set-back now.

Draft Policy EN7 (Sustainable Drainage) and householder schemes

Draft Policy EN7 would make SuDS a requirement well below the major threshold. Part 1 reads: “All major developments and developments involving new buildings must incorporate Sustainable Drainage Systems (SuDS), unless evidence is provided to show they are inappropriate.” The reasoned justification (8.102) excludes extensions and change of use applications from that duty. Part 6 expects permeable paving in all hardstanding, with a sub-base or attenuation system on clay, and part 7 asks for a positive pumped device on any new basement connected to the sewer (Regulation 19 draft, chapter 8). For a new house on a garden plot, that means a SuDS strategy where today none may be asked for at validation.

Triggers for each report on a Royal Greenwich application

A flood risk assessment, a sequential or exception test and a SuDS strategy answer different questions, and each has its own trigger in Greenwich. The table joins up the NPPF, the validation list, the SFRA and the draft policies.

One line in the validation list matters most to an applicant who has checked only the national map. In the standing advice section it says that the “Surface water flood extent from the Environment Agency’s modelling and Royal Greenwich’s SFRA to be treated the same as in Flood Zone 3.” A dry Flood Zone 1 site with a surface water flow path across it is therefore assessed as though it sat in the floodplain. The explainers on when a flood risk assessment is needed and critical drainage areas give the national position, and the Flood Risk Map is a quick first check of the flood zone for any address.

Drainage evidence the council's flood team expects

As Lead Local Flood Authority, Greenwich wants surface water to leave a site at greenfield rates, evidence for every step of the hierarchy and a completed SuDS proforma. The standards are spread over three documents: the 2026 SFRA (section 6.6.3), the Local Flood Risk Management Strategy approved by Cabinet on 23 September 2026 (section 3.8), and the validation list. The council's flood risk guidance for developers page still links the October 2015 guide, so the 2026 documents are the ones to work from.

• Discharge rate. Greenfield, or as close to greenfield as reasonably possible, with the 1 in 100 year plus climate change event attenuated on site (LFRMS 2026, section 3.8). The SFRA asks for significant betterment on brownfield rates, and the Climate Resilience SPD asks householder schemes to reduce runoff in proportion to their size.
• Storm events. The proforma records greenfield, existing and proposed rates for the 1 in 1, 1 in 30 and 1 in 100 year events, the last with a 40% climate change allowance, with the storage each needs (SFRA 2026, section 6.6.3). The Environment Agency's peak rainfall allowances sit behind that figure.
• Infiltration. The validation list wants intrusive testing for infiltration rates, groundwater levels and contamination wherever infiltration SuDS are proposed. The SFRA allows a desktop feasibility study at application stage, with BRE 365 testing secured by condition, at the council's discretion; the BRE 365 infiltration rate calculator and the geology and soakaway map help judge it early.
• Sewer connections. Thames Water's in-principle agreement and written confirmation that the network has capacity, with evidence that the receiving system can take the flow.
• National Standards. The SFRA and draft EN7 both expect the strategy to meet the National Standards for Sustainable Drainage Systems published by Defra in 2025, which NPPF policy F8 now names.
• Maintenance. A plan showing how the system will be looked after for the lifetime of the development and who adopts each part of it.

We prepare the strategy and the proforma together, so the rates and volumes in one match the other. A mismatch between them is an easy objection to avoid. The SuDS proforma explainer and the drainage calculators show the numbers involved.

Thamesmead: no new connections to a system at capacity

The SFRA treats the Thamesmead catchment as a special case. Its first recommendation is that “New developments should avoid connecting to the existing surface water drainage system within the Thamesmead catchment area, as it is currently at capacity.” Schemes reusing an existing connection must discharge at greenfield rates, connections in the wider Marsh Dykes catchment that drain to Thamesmead are scrutinised more closely, and new development is expected to contribute to the strategic SuDS network (SFRA 2026, section 7.6.3). On a Thamesmead site the drainage strategy has to find somewhere for the water other than the pipe at the boundary, and that question shapes the layout. Our Thamesmead page explains how the town divides between Greenwich and Bexley.

The July 2026 SFRA, the validation list and the Climate Resilience SPD

Three council documents changed or were confirmed in the last eighteen months, and each one adds something the national maps do not.

• Strategic Flood Risk Assessment (June and July 2026). Level 1 report version 1.1 (July 2026) and Level 2 report version 1.1 (June 2026), both by Metis Consultants, replacing the 2017 and 2018 SFRAs. They map all sources on an online web map, carry the Thames breach model results, and give a groundwater screening approach for basements. At Level 2 they screen 56 potential sites and assess 43 of the draft allocations in detail. Finished floors are expected 600 mm above the 1 in 100 year plus climate change level for most uses, reducible to 300 mm only where the flood level is known with high certainty. Documents on the council's SFRA page.
• Local Validation Requirements List (June 2025). Sets the flood risk assessment triggers in the table above, requires a SuDS Strategy on every major application, a Basement Impact Assessment for basements beside homes, and, for major schemes, a foul sewage and utilities assessment that keeps space for plant access and future raising of the flood defences.
• Climate Resilience SPD (adopted 25 March 2026). Replaces the Greener Greenwich SPD. It asks for SuDS from the outset of a scheme, 10 to 15 mm of source control, permeable surfaces in place of hardstanding, and early contact with the council's lead flood risk officer to confirm greenfield rates.

The SFRA predates the August 2026 NPPF and cites the 2025 version of the PPG, so a flood risk assessment today applies the current Framework and uses the SFRA for the local evidence. The SFRA explainer covers what these documents are for, and the guide to applications invalidated over flood risk and drainage sets out the validation pitfalls.

Chapter 18 of the NPPF on Greenwich's defended floodplain

National policy is the National Planning Policy Framework of 17 August 2026, whose Chapter 18 (Managing flood risk and coastal change) sets the tests in policies F1 to F9. Policy F4 sets when a site-specific assessment is needed, including on land an SFRA identifies at risk from any source; F5 is the sequential test and F6 the exception test; F7 asks that development be safe for its lifetime with residual risk managed under an agreed emergency plan; and F8 requires SuDS designed to the 2025 National Standards. The Planning Practice Guidance on flood risk and coastal change, last updated in September 2025, and the Flood Map for Planning sit underneath.

In Greenwich the national tests meet a riverside where much of the land is in Flood Zone 3 and all of it is defended. F7's emergency plan and residual risk wording lines up with Policy E3, and the SFRA's breach data is what makes both answerable. Our NPPF guidance page sets out the August 2026 policy letters in full.

Where flooding comes from in the Royal Borough

Tidal flooding from the Thames is the dominant risk. The borough's 13.7 km of riverside sits behind river walls and the Thames Barrier at New Charlton, and the council's strategy expects the Barrier to need replacing by 2070. Under Thames Estuary 2100 the frontage falls into two policy units, Greenwich from Deptford to the Woolwich Ferry Terminal and Thamesmead from the ferry to Erith Pier. The SFRA records a tidal range of more than seven metres on spring tides. Our River Thames page and the Thames Barrier article give the background, and the live river levels map shows the gauges.

Inland, the Ravensbourne and Deptford Creek bring fluvial risk in the west and the Quaggy in the south, where the 1968 flood reached Blackheath Park and Eltham Green. Surface water and blocked drainage caused the floods the council has investigated recently. Homes on Woodbrook Road and Waterdale Road flooded in November 2022 after a trash screen on the Marsh Dykes blocked, and a borough-wide Section 19 investigation of the November 2023 to May 2024 events at King John's Walk, Nathan Way and Plumstead Road. Thames Water's assessments flag sewer surcharging around Deptford, Thamesmead, North Greenwich and Plumstead.

Each place is covered in more depth on its own page: flood risk assessment in Greenwich, Woolwich, Thamesmead (linked above) and neighbouring Deptford, most of which lies in Lewisham. Across the river, Barking and Dagenham sets its own requirements.

Reports we prepare for applications to the Royal Borough of Greenwich

We prepare flood risk assessments, sequential and exception tests and drainage strategies for Greenwich applications. They are three separate reports: the assessment asks whether the site is safe, the sequential test asks whether a lower-risk site was available, and the drainage strategy shows where the water goes. A riverside scheme in Greenwich can need all three, written so that each answers its own policy.

• Flood risk assessment. Policies E2 and E3 ask for one wherever the SFRA or the validation list puts the site at risk, from a Flood Zone 3 rear extension to a Peninsula tower: flood risk assessment.
• Planning applications. Breach levels, floor levels and the flood plan, set out against each part of E2 and E3 and the draft EN6 limits: flood risk assessment for planning.
• Buying a riverside home. Much of the Peninsula and Thamesmead is defended Flood Zone 3, which lenders and searches flag: flood risk survey for property purchase.
• Windfall sites in the floodplain. Sites outside the new plan's allocations follow section 6 of the SFRA for the sequential test: sequential and exception test.
• Drainage for any scheme with a new building. Greenfield rates under SI 13 and the SuDS proforma from the SFRA: drainage strategy.
• The SuDS strategy and proforma. Rates for the 1 in 1, 1 in 30 and 1 in 100 year events, storage, the hierarchy evidenced and the maintenance plan: surface water drainage strategy.
• After permission. The SFRA lets the council secure BRE 365 infiltration testing by condition, so the final calculations often follow consent: discharge of drainage conditions.
• Foul drainage. Draft EN7 and the validation list ask for early contact with Thames Water on capacity: foul drainage strategy.
• Flood plans. Policy E3 requires a flood plan with evacuation procedures, and the SFRA asks major schemes on dry islands for an emergency plan: flood warning and evacuation plan.
• Basements. The SFRA asks for a groundwater screening study with borehole levels, and puts groundwater risk highest near Woolwich and around Sutcliffe Park: groundwater flood risk assessment.
• Non-residential schemes. The validation list asks for a BREEAM pre-assessment targeting Excellent: BREEAM flood risk assessment.
• Riverside commercial land. Charlton Riverside and the Peninsula carry industrial and retail land in Flood Zone 3: flood risk due diligence.
• Homes that have flooded. The council's Section 19 reports record internal flooding on Woodbrook Road and in Plumstead: flood risk assessment for insurance.

Our chartered consultants write each report to the council's 2026 evidence base. Reports for applications to the Royal Borough of Greenwich come from Unda Consulting Limited, a CIWEM Business Partner. Requirements for other boroughs are in the local authority guides, and the London page brings the capital's councils together.

Frequently asked questions about Royal Greenwich flood risk and drainage requirements

Unda Consulting Limited prepares flood risk assessments and drainage strategies for applications to councils across England. To discuss a site in the Royal Borough of Greenwich, call 01293 214444 or email enquiries@unda.co.uk.